Luxman’s gear has always performed well, but their vintage gear from the 70s is much more sought after than their gear in the 80s. In the early 80s Tim de Paravicini already walked away from designing for Luxman, and Alpine bought them, and they no longer reigned. But the gear was still pretty good. $5 is a steal for the unit you got.
When I first started out, Luxman was my starting point, and I recapped a number of their integrateds and amps, including the Luxman L-450, L-80V, L-85V (which i still have), and the M-300. The L-85 and M-300 are very good if able to restore.
Congratulations on your purchase!